Even after having proofread my thesis many times, I think asking another person to proofread it before submission is necessary.
Is it considered cheating to ask a friend or tutor to proofread your thesis before submission?
No. The purpose of your thesis review is not to test your ability to use a word processor or to compose text in a social vacuum. It is a test of your ability to conduct research and communicate those findings to others. Treat it like you would treat any publication, and get feedback from your peers in order to make it as good as possible.
No, not at all! Every writer needs readers, and the purpose of those readers is, as already mentioned, to find the errors, typos, and unclear sections that are now invisible to the writer who has seen the manuscript a thousand times.
Obviously, if your friend or tutor is actually providing content for you, and you are not acknowledging their contribution, then that IS cheating. When you ask someone to read for you, be sure to tell them exactly why you need another set of eyes on the manuscript. I usually ask my friend (or supervisor, if willing) to simply flag all typos and mark the margin where a paragraph is less than clear to them. I can usually figure out what is wrong without having them actually give me any content.
I find that writing--at least good writing!-- is usually not a solo effort, and I am always indebted to at least one person for taking the time to read my manuscript and flag the problem spots for me.
If your thesis is in math, by all means have others proofread it. Once it is released, it will no longer be possible to correct an error!
However, if your proofreader finds something more substantial than a typing or simple mistake, you must not only credit him with his ideas on the acknowledgement page, but also in a footnote. No harm in this. It is better to get it right and give credit than to get it wrong and take the credit for that for yourself! The quality of your work also reflects on the reputation of your project director and your committee members, you have to respect them by turning out a high quality product.
However, I have found that the probability of a totally error-free thesis is equal to or less than the smallest positive number.
I cannot advise those whose who are English majors; that is a foreign language to an engineer!